Thermo-hydrological numerical evaluation of carbon dioxide injection efficiency for its geologic storage using a coupled reservoir-well simulation scheme

Abstract

A coupled reservoir-well simulation scheme is established to analyze quantitatively multi-phase fluid flow and heat transport due to carbon dioxide (CO2) injection in a reservoir rock-injection well system and to evaluate rigorously the CO2 injection efficiency in terms of the CO2 injection rate and injectivity. Two different cases of the CO2 injection pressure and temperature at the well head are then simulated using the coupled reservoir-well simulation scheme within a multi-phase thermo-hydrological numerical model. The results of the numerical simulations show that the fluid pressure and temperature and the CO2 injection rate and injectivity in the reservoir rock-injection well system can be quantitatively evaluated using the coupled reservoir-well simulation scheme. The fluid pressure and temperature in the injection well including the well head and bottom can also be simply predicted with assumptions of the hydrostatic fluid pressure transition and the adiabatic fluid temperature transition from the well head to the well bottom using the thermodynamic equation of state (EOS) data of CO2. In addition, the CO2 injection rate and injectivity have very close relationships with the fluid pressure and temperature at the well bottom, respectively, which determine the fluid pressure difference between the injection well bottom and the far-field reservoir rock and the kinematic viscosity of CO2 at the well bottom. The CO2 injection rate increases almost linearly with the fluid pressure difference, whereas the CO2 injectivity varies unsystematically with it. Instead, the CO2 injectivity has an excellent linear relationship with the reciprocal of the kinematic viscosity (i.e., kinematic fluidity) of CO2. These results can be utilized as practical guidelines to determine optimal injection operation schemes for sustainable, safe, and efficient geologic storage of CO2.